1. Field of the Invention
This invention relates in general to pack frames and in particular to pack frames formed of plastic tubing assembled in part by heat shrinking sections of tubing together whereby the frame members are fixedly but flexibly interconnected with each other at joints adapted to give without fracturing or disengaging under the application of above normal force thereto.
2. Description of the Prior Art
Prior pack frames constructed of polyvinyl chloride tubing normally involved gluing the frame members together by means of conventional setting glue or plastic cement. During the assembly of the pack frame members, a set or cure period for the glue was necessary when the members were initially interconnected. The bond thus formed between the frame members was relatively rigid and incapable of flexing without fracturing beyond the degree of flex inherent in the tubing material itself when subjected to stress such as that occurring when the pack frame was accidentally dropped with a loaded pack bag thereon. When repeatedly subjected to such stresses, as would normally occur during extended use in a recreational environment, the portions of the tubing forming the connections or joints between frame members sometimes developed hairline fractures which weakened and occasionally rendered the pack frame unserviceable.
My prior patent, U.S. Pat. No. 3,734,366 discloses a pack frame constructed from plastic tubing material including tee connectors slidably mounted on vertical frame members and glued to cross members.
U.S. Pat. No. 3,860,157 discloses a plastic tubing pack frame employing a stretchable netting extending between the upstanding parallel legs to hold the frame members in engagement with each other.